i have a 99 gsr and i want to buy a dc 4-1 header with a two and a half inch collector. Does anyone know how much it would cost to get a flange that size welded to my cat? Also, is the header with a 2 1/2 inch that much better then 2 and 1/4? thanks

 

Why do you want a 2.5" collector on that header?

The biggest I'd go on that motor would be 2.25" anyways.

 

The stock GSR engine doesn't flow enough to necessitate the larger collector, and you won't really be benefiting from it without going to a larger exhaust anyway.

 

...he could still do it nonetheless.

AllM0tadc2, You'll have to visit a local muffler shop and ask them, cuz every muffler shop prices vary when it comes to this kind of exhaust work...